When Jesus was asked, “Which is the great commandment in the Law?” he replied, “You shall love the Lord your God with all your heart and with all your soul and with all your mind. This is the great and first commandment” (Mt 22:36-37).
As we near the end of John Flavel’s Keeping the Heart, Flavel offers both warnings and encouragements. We begin with his warnings. He writes, “You have heard that the great work of a Christian is to keep the heart, in which the very soul and life of Christianity consist. And this work is the foundation of all acceptable duties to God.”
Just as Jesus declared, genuine Christianity—that is, genuine faith, discipleship, and even salvation—cannot exist without the heart’s involvement. “You shall love the Lord your God with all your heart and with all your soul and with all your mind” (Mt 22:37). Notably, Jesus does not mention the body. He does not say, “You shall love the Lord with all your body,” or “all your behaviors and activities.” This omission does not suggest that our bodily actions are irrelevant. Instead, it reflects two truths: what we do in the body flows from the heart, and without the heart, our actions are devoid of meaning.
Consider Paul’s words about love in 1 Corinthians 13:
If I speak in the tongues of men and of angels, but have not love, I am a noisy gong or a clanging cymbal. And if I have prophetic powers, and understand all mysteries and all knowledge, and if I have all faith, so as to remove mountains, but have not love, I am nothing. If I give away all I have, and if I deliver up my body to be burned, but have not love, I gain nothing. (1 Corinthians 13:1-3)
Paul’s message is clear: righteous actions without sincere motivation are worthless. Consider a wealthy businessman seeking to enhance his company’s reputation. He might donate thousands, even millions, to charity, but for entirely self-serving reasons. He gives not from love, not to please God, perhaps not even from genuine concern for the charity he supports. He gives to benefit himself. His actions may be right, but his heart is wrong, rendering his actions meaningless. Worse, he becomes a hypocrite of the worst kind.
As Flavel reminds us, “The great work of a Christian is to keep the heart, in which the very soul and life of Christianity consist. And this work is the foundation of all acceptable duties to God.”
This theme resonates throughout Israel’s history. The Lord, through the prophet Joel, warns the people of Judah, “Return to me with all your heart, with fasting, with weeping, and with mourning; and rend your hearts and not your garments” (Joel 2:12-13).
What prompts this warning? Are the people of Judah engaged in blatant sin? Are they neglecting proper sacrifices or failing to observe the Sabbath? Joel mentions no particular transgression. Instead, he accuses them of spiritual apathy. They have grown complacent; their love for God has grown cold. They may continue going through the motions of their religion, but something remains terribly wrong.
Notice Joel’s prescription: “Return to me with all your heart” (Joel 2:12). Yes, they should fast and weep, but certainly not for appearance’s sake. God declares, “I want your heart. Return to me with all your heart.” Then he adds specifically, “Never mind rending your garments.” Even a wild animal can tear clothing. “No,” he says, “Rend your hearts. I want your hearts to repent.”
This desire for authentic hearts has remained constant throughout God’s dealings with his people. When we examine the sins and rebellions of Israel in the Old Testament, the underlying issue was always the heart, which is why the new covenant spoken of by Ezekiel, Jeremiah, and the prophets always addressed the heart. “And I will give them one heart, and a new spirit I will put within them. I will remove the heart of stone from their flesh and give them a heart of flesh” (Eze 11:19).
Without a changed heart, all external reforms prove meaningless. This truth is powerfully demonstrated in the New Testament during Christ’s ministry.
Consider the Pharisees, those religious leaders of the first century. Nearly two hundred years before Christ, the Pharisees emerged as a grassroots movement opposing Greek Hellenism and pagan influence in Israel. They believed in serving God and maintaining obedience to his commandments despite the shifting culture. In short, their origins were commendable. They were the people who remained faithful to God while most of the nation allowed pagan influence to take root.
But what happened? When John the Baptist begins his ministry, he quickly indicts the Pharisees. In Matthew 3, he declares, “You brood of vipers! Who warned you to flee from the wrath to come? Bear fruit in keeping with repentance” (Mt 3:7-8). Repentance? What does John mean by repentance? Were they not the repenters? Were they not the people who remained loyal to God while everyone else fell away to some degree? Yes and no.
The Pharisees may have remained loyal by all appearances, but they were just as far from God as anyone else. When Jesus began speaking about them during his ministry, he continually referred to them as hypocrites. In his Sermon on the Mount, he teaches the people to pray, tithe, and fast, but not like the Pharisees. Why? They were hypocrites. Yes, they prayed, tithed, and fasted, but they were performing empty rituals.
Consider the Pharisee who went into the temple to pray. He could boast of all his good works and the fact that he was not a blatant sinner like the tax collector who was also in the temple praying, but Jesus said he was not justified. His faith was not authentic. He was a hypocrite. He made a good show of righteousness, but it was all for nothing because the most essential element was missing—the heart.
Flavel writes:
Oh, how many hours have some professing Christians spent in hearing, praying, reading, and confessing? And yet, as to the main end of religion, it would have been as good for them to have sat still and done nothing; for all this signifies nothing when the great work, heart work, is all the while neglected. Tell me, vain pretender, when did you shed a tear for the deadness, hardness, unbelief, or earthliness of your heart? Do you think that such an easy religion can save you? If so, we may invert Christ’s words and say wide is the gate and broad is the way that leads to life, and many there are that enter in. Hear me, you self-deceiving hypocrite, you who have put off God with heartless duties, who have acted in religion as if you had been worshipping an idol that could not search and discover your heart, and who have offered to God only the skin of the sacrifice but not the marrow, fat, and meat of it: how will you abide the coming of the Lord?
This is strong language, but rightfully so. Remember that no one in the Bible spoke more about hell than Jesus, and he was ministering among religious Jews, not pagan Gentiles. When he warns about the reality of hell, he is not speaking directly to people who worship idols or false gods. He is not speaking to people who openly reject Yahweh, the one true God. He is speaking to God’s covenant people who claim to love God and keep his law. And yet, he warns of hell more often than anyone else in Scripture.
As Jesus brings his Sermon on the Mount to a close, he says this:
Enter by the narrow gate. For the gate is wide and the way is easy that leads to destruction, and those who enter by it are many. For the gate is narrow and the way is hard that leads to life, and those who find it are few. (Matthew 7:13-14)
Every healthy tree bears good fruit, but the diseased tree bears bad fruit. A healthy tree cannot bear bad fruit, nor can a diseased tree bear good fruit. Every tree that does not bear good fruit is cut down and thrown into the fire. Thus you will recognize them by their fruits.
Not everyone who says to me, “Lord, Lord,” will enter the kingdom of heaven, but the one who does the will of my Father who is in heaven. On that day, many will say to me, “Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?” And then I will declare to them, “I never knew you; depart from me, you workers of lawlessness.” (Matthew 7:17-23)
Three sobering truths emerge from this passage.
First, Jesus warns that most people are not on the path that leads to life—a sobering thought that should immediately arrest our attention.
Second, he declares that people will be known by the fruit they bear. Specifically, he teaches that people will bear fruit according to their nature. A bad tree produces bad fruit; a good tree produces good fruit. Or, evil comes from an evil heart, while righteousness comes from a righteous heart.
That principle seems straightforward enough, but notice the third lesson: not everyone who appears to bear good fruit is actually bearing good fruit. Have you ever bought produce from the grocery store only to discover it was rotten on the inside? That is what Jesus says will be revealed about many people. They will have done good works in his name. They will have preached in his name. They will have called him Lord. In fact, they will have been emphatic about it: “Lord, Lord,” they say. But in the end, Jesus will say to them, “I never knew you; depart from me, you workers of lawlessness” (Mt 7:23).
This passage is terrifying. Naturally, we want to know where they went wrong. They appeared to be doing everything right. We could argue that they themselves believed they were doing everything right. So what happened?
Jesus provides the answer in his later confrontation with the Pharisees:
Woe to you, scribes and Pharisees, hypocrites! For you clean the outside of the cup and the plate, but inside they are full of greed and self-indulgence. You blind Pharisee! First clean the inside of the cup and the plate, that the outside also may be clean.
Woe to you, scribes and Pharisees, hypocrites! For you are like whitewashed tombs, which outwardly appear beautiful, but within are full of dead people’s bones and all uncleanness. So you also outwardly appear righteous to others, but within you are full of hypocrisy and lawlessness. (Matthew 23:25-28)
Jesus emphasized this same truth in his conversation with Nicodemus the Pharisee: “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God” (Jn 3:3). This statement confounded Nicodemus. “How can a man be born when he is old? Can he enter a second time into his mother’s womb and be born?” (Jn 3:4).
Of course, Jesus was not speaking about physical birth. He was describing spiritual, internal birth—a contrite heart turning to the Lord in faith, knowing it has no hope apart from Christ. He was referring to a person whose very nature has been changed by the Holy Spirit. Public religion will come later. Jesus declares we need private and personal reformation within.
Flavel writes, “Oh, tremble to think what a fearful judgment it is to be given over to a heedless and careless heart, only using religious duties to quiet and still your conscience!”
This was Israel’s problem in the Old Testament. This was the Pharisees’ problem in the New Testament. And this remains the problem for many religious people today. Hypocrites abound in churches around the world, and I use that word in its truest sense—someone who appears to be something they absolutely are not.
This is why Paul, writing to a Christian church (albeit a church with its fair share of moral problems), can say, “Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that Jesus Christ is in you?—unless indeed you fail to meet the test!” (2Co 13:5). The King James Version renders this memorably: “Know ye not your own selves, how that Jesus Christ is in you, except ye be reprobates?”
Paul might have said, “Examine your hearts. Do not tell me how often you go to church, or read your Bible, or give money to the poor, as important as those things are. Open up that fruit. What is on the inside? Where is your heart?”
To be clear, this is not intended to cripple a genuine believer with fear that they may not be saved. These warnings by Flavel, not to mention Scripture, are intended for precisely what Proverbs 4:23 says: “Keep [or guard] your heart with all vigilance.”
Flavel writes:
Here, I also conclude—to the shame of even upright hearts—that unless the people of God spend more time and labor on their hearts than they ordinarily do, they are never likely to do God much service or to attain much comfort in this life.
He goes on to say two things have “eaten up the time and strength of the Church in this generation and sadly diverted us from heart work.”
These two things are fruitless controversies and earthly encumbrances. This list is by no means exhaustive.
First, by fruitless controversies, he means those trivial matters we often fight about or consume ourselves with in the church. As he wisely observes, “Oh, how much better it is to see believers live rightly than to hear them dispute subtly.”
Second, and perhaps more pertinent, he mentions earthly encumbrances. He writes:
The heads and hearts of many have been so filled with the noise of worldly business that they have sadly and sensibly declined and withered in their zeal, love, and delight in God and in their ability to talk seriously and profitably about heavenly things with others.
The implication in all of this is that we are failing to tend to our hearts. We are treating our hearts as we would never treat our bodies. If you fail to feed your body, it starves to death. Imagine what happens to the heart, from which “flow the springs of life,” if we starve it (Pr 4:23).
Therefore, as Flavel encourages us to do, tend to your heart. Do not neglect the heart. He writes:
Oh, study your hearts, watch your hearts, and keep your hearts. Rid yourselves of fruitless controversies and idle questions, empty titles and vain performances, unprofitable debates, and bold censures of others. Turn in upon yourselves, get into your prayer closets, and then resolve to dwell there. For too long, you have been strangers to this work, kept other vineyards, and trifled around the borders of Christianity. For too long, this world has detained you from your great work. Will you now resolve to look more to your hearts? Will you hurry and come out of the crowds of business and the clamors of the world to spend time with God more than you have done? Oh, that this would be the day you would resolve to do it!
He goes on to suggest that we pause every night and ask ourselves, “Oh, my heart, where have you been today? Where have you traveled today?”
Now, let us turn to consider Flavel’s encouragements. He offers ten motives to keep our hearts—ten spiritual blessings, we might say, if we strive to keep our hearts.
1. Increased Spiritual Understanding
We all understand that there exists a difference between having knowledge of something and truly knowing or understanding it. I will offer an example from my own life.
I was a professing Christian and was baptized at the age of eleven. I stood up in front of the entire church and confessed that I was a sinner whom only Christ could save. But it was not until years later that my sinfulness actually broke me. It was not until years later that I experienced a sincere godly sorrow over my sin. I was in my early twenties before I called out to the Lord for salvation. When I was eleven, I knew what the gospel and salvation were all about. I knew it in my head, that is. But it took me another decade before that understanding reached my heart.
This is why Paul prays as he does in Ephesians chapter 1. He says to the believers in Ephesus, “May [God] give you the Spirit of wisdom and of revelation in the knowledge of him, having the eyes of your hearts enlightened” (Eph 1:17-18).
He does not want them to know something merely. Anyone can read the Bible and learn the facts. I have known some staunch unbelievers who know the Bible better than many Christians. But head knowledge is not the same as heart knowledge, so Paul prays that the Ephesians’ hearts would be enlightened. And it is only after God reveals things to our hearts that we truly understand.
I was talking with someone the other day about an unfortunate situation he was in. Quite naturally, he was looking for a solution to his problem by suggesting ways he could change the circumstances. If only this would happen, then things would get better. So, I pointed him to 2 Corinthians 12. That is where Paul has a thorn in his flesh, which he pleads with God to take away. But God says no. He says, “My grace is sufficient for you, for my power is made perfect in weakness” (2Co 12:9). In other words, Paul’s circumstances did not change at all. He still had the thorn. He was still suffering. Nothing external changed at all.
And yet, what does Paul say in response? “I will boast all the more gladly of my weaknesses, so that the power of Christ may rest upon me” (2Co 12:9). The King James goes as far as to have Paul say, “Therefore I take pleasure in infirmities” (2Co 12:10).
What changed for Paul? If not his circumstances, what changed?
His understanding. We might say the Lord opened the eyes of his heart to know both the power of Christ in his weakness and God’s ordained purpose for his weakness. Regardless, his understanding deepened without any external means. He learned it in his heart.
2. Protection from Errors
Flavel writes about this blessing:
The study and observation of your own heart will inoculate you against the dangerous and infecting errors of the times and places that you live in. … What is the reason that so many thousands have been led away by the errors of the wicked? And why have those who have sown false doctrines had such a plentiful harvest among us? It is because they have met with a company of empty, nominal believers that never knew what belongs to practical godliness and the study of their own hearts.
I think about this whenever I see one of these video clips circulating online of a lesbian pastor wearing a rainbow flag, talking about how God is a woman, the resurrection was a hallucination, and other very blasphemous ideas. I hear this and think, Who is getting up every Sunday morning to go to this place, hear this nonsense, financially support it, and be a part of it? While I can comprehend someone wanting to hear what they want to hear, many churches today—so-called churches—have utterly dismantled the Bible and destroyed the Christian faith. I am left asking, why bother with any of it? What is the point of the church?
If nothing else, it provides an example of what heartless Christianity can descend into—how far it can deviate from the truth of God. If these video clips I have seen are any indication, a heartless form of Christianity can destroy common sense itself. Why would anyone profess to be a disciple of Christ when they reject his word, do not believe he was God, and deny his resurrection? It defies all logic.
That is an extreme example, of course, but the point is that an unguarded heart is like a boat without an anchor. To avoid, as Paul said, being “tossed to and fro by the waves and carried about by every wind of doctrine, by human cunning, by craftiness in deceitful schemes,” we need hearts that we have examined, humbled, and allowed the Word of God to shape (Eph 4:14). We need to safeguard our hearts against cultural pressures and even personal desires.
3. Assurance of Salvation
What separates a genuine Christian from a religious hypocrite who merely professes to be a Christian? What is the difference between a truly saved person and an unsaved person who may sit next to you on the pew every Sunday? What separates the true Christian from those people described by Jesus in Matthew 7 who behaved like disciples but were, in fact, unrighteous, hell-bound sinners?
Once again, it is the heart. Listen to Flavel on this point:
It is amazing to consider how far hypocrites will go in all external duties and how plausibly they can order the outward man, hiding all their indecencies from the observation of the world, but they take no heed to their hearts. They are not in secret what they appear to be in public.
One of the best means of being confident of your salvation is to examine, not your works, but your heart. Will you find devotion and sincerity? What motivates you to do the works you are doing?
4. Increased Joy in Your Duties
In a previous chapter of his book, Flavel said, “A heart seasoned with grace makes every duty pleasant.”
The more the heart seeks God, pines for God, pursues God, and is kept guarded from everything else, the more we will want to seek him, and the more enjoyable it will be.
In the denomination of my upbringing, there was a tradition where visiting preachers, invited or not, would almost always be invited to preach if they showed up for a Sunday morning service. So, let’s say one was traveling and stopped at a church away from home. If the pastor knew him or discovered he was a preacher, he would be asked to preach. “Preach the word; be ready in season and out of season,” right? (2Ti 4:2).
Now, I have thoroughly enjoyed preaching and teaching for years, but I quickly learned that when you are not quite prepared, preaching feels more terrifying than enjoyable.
This principle applies to all our spiritual duties. Consider Psalm 40: “I delight to do your will, O my God; your law is within my heart” (Ps 40:8). Having God’s law in his heart caused David to feel delight when keeping that law.
5. More Focused Prayers
Flavel argues that self-knowledge provides inexhaustible material for prayer:
Acquaintance with your own hearts can also be a fountain that supplies you in prayer. Those who are diligent in heart work and know the state of their own souls will have an overflowing fountain of praises and prayers to supply them in all their addresses to God. The tongue will not falter for something to pray.
Scripture confirms this principle. The psalmist declares, “My heart overflows with a pleasing theme; I address my verses to the king; my tongue is like the pen of a ready scribe” (Psalm 45:1). Jesus himself taught that “out of the abundance of the heart his mouth speaks” (Luke 6:45).
According to Flavel, prayer rooted in genuine self-examination differs markedly from rote recitation:
When you are experienced with your heart and mourn before God over a specific heart corruption or wrestle before God for the supply of some special inward need, you do not speak as others do who have learned to pray by rote; their confessions and petitions are squeezed out, but yours drop freely like pure honey from the comb.
6. Recovery of Spiritual Power
Flavel’s deep concern for the spiritual superficiality of his era permeates this chapter. He laments the prevalence of nominal Christianity and envisions a different reality:
In this way [by examining and keeping the heart], the decaying power of Christianity will be recovered again among believers, which is the most desirable sight in this world. Oh, that I might live to see that day, when Christians will not walk in a vain show, when they will no longer please themselves with the appearance of life while being spiritually dead, and when they will no longer be (as many are now) a company of superficial, vain persons. Instead, the majestic beams of holiness will shine from their heavenly and serious speech that will awe the world and command reverence from everyone around them. And they will warm the hearts of all who come near to them so that everyone will say, “God is truly in these people.”
For Flavel, the church’s testimony depends upon its members engaging in what he consistently terms “heart work”—the diligent examination and cultivation of inner spiritual life.
7. Removal of Stumbling Blocks
Flavel establishes a direct connection between inner negligence and outward scandal: “A neglected, careless heart must necessarily produce a disordered, scandalous life.” He continues with urgent exhortation:
Oh, professors! If you are ever to keep religion sweet and if you ever hope to recover your testimony in the world, keep your hearts! Either keep your hearts or lose your testimony. Keep your hearts or lose your comforts. Keep your hearts lest you shed the blood of souls. What words can express the deep importance and the wonderful consequences of this work? Everything reveals it to be necessary, serious, and beautiful.
The logic is unavoidable: since “from [the heart] flow the springs of life,” an unguarded heart inevitably produces the very stumbling blocks that compromise Christian witness (Pr 4:23).
8. Preparation for the Future
Paul’s example in 1 Corinthians 9 illustrates the necessity of continual self-discipline. He declares, “I discipline my body and keep it under control, lest after preaching to others I myself should be disqualified” (1Co 9:27). Despite his faithful service, Paul recognized that future effectiveness required present vigilance. Without attention to his inner life, he risked disqualification from the very ministry God had entrusted to him.
This principle extends beyond apostolic ministry. Paul writes in 2 Timothy 2:21, “If anyone cleanses himself from what is dishonorable, he will be a vessel for honorable use, set apart as holy, useful to the master of the house, ready for every good work.” Flavel warns of the consequences when this preparation is neglected:
Consider a man who has not learned to keep his heart. If you give him any service for God that is attended with honor, it will swell up his spirit in pride. If you give him suffering, it will depress and sink him.
Most believers have witnessed, if not experienced, this spiritual unpreparedness firsthand.
9. Closer Fellowship with Other Believers
I unintentionally missed #9 in the original teaching. As Flavel writes, “If the people of God would more diligently keep their hearts, consider how the fellowship of saints would be exceedingly sweetened!”
10. Increased Benefit from Spiritual Duties
Flavel identifies a common frustration among Christians: the inability to maintain spiritual momentum after experiencing meaningful worship.
By keeping your heart, the comforts of the Spirit and the precious influences of all the ordinances would be established and much longer preserved in your soul than they are now. Ah! What would I give for my soul to be preserved in the frame that I sometimes find it in after an ordinance! Sometimes, Oh Lord, … You admit me into the most inward, unusual, and sweet delights … But alas! The heart grows careless again and quickly returns, like water removed from the stove, to its native coldness. If you could only keep those things forever in your hearts, what Christians would you be! What lives would you live!
Flavel diagnoses the problem with characteristic insight:
But how is it that these things do not remain longer with us? Doubtless, it is because we allow our hearts to become cold again. We should be as careful after an ordinance or spiritual duty to prevent this as one that comes out of a hot bath is of going into the chill air. We have our hot and cold fits in their turns, and what is the reason but our unskillfulness and carelessness in keeping the heart.
Many believers recognize this pattern: Sunday worship leaves them spiritually nourished and excited, yet by Monday, they feel spiritually cold again. Rather than passively waiting for the next service to restore spiritual warmth, Flavel advocates active heart maintenance—staying oriented toward heavenly things, maintaining communion with God, and vigilantly guarding against the heart’s enemies.
Flavel concludes with a compelling summary of heart-keeping’s benefits:
Look over these ten special benefits and weigh them on just scales. Are they small matters? Is it a small matter to have your weak understanding assisted, your endangered soul cured, your sincerity cleared, your communion with God sweetened, and your sails filled in prayer? Is it a small thing to have the decaying power of godliness again restored, to have all fatal scandals removed, to gain an instrumental fitness for serving Christ, to restore the communion of saints to its original glory, and to have the influences of the ordinances abiding in the souls of saints? If these are no common blessings or small benefits, then surely it is a great duty to keep the heart with all diligence.